Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantos canais terrestres digitais existem para o canal 4?
 ###Tabelas: CREATE TABLE 1980–1989 (1980–1989_id AUTO_INCREMENT PRIMARY KEY, January VARCHAR, February VARCHAR, March VARCHAR, April VARCHAR, June VARCHAR, July VARCHAR, August VARCHAR, September VARCHAR, October VARCHAR, November VARCHAR, December VARCHAR) CREATE TABLE availability_of_channels_from_various_providers (availability_of_channels_from_various_providers_id AUTO_INCREMENT PRIMARY KEY, Position INT, Channel VARCHAR, Analogue terrestrial channel VARCHAR, Digital terrestrial channel VARCHAR, Internet VARCHAR) CREATE TABLE 2012_draft_picks (2012_draft_picks_id AUTO_INCREMENT PRIMARY KEY, Round INT, Overall VARCHAR, Player VARCHAR, Position VARCHAR, Nationality VARCHAR, Club team VARCHAR) CREATE TABLE global_challenge_2004_5 (global_challenge_2004_5_id AUTO_INCREMENT PRIMARY KEY, Overall place VARCHAR, Yacht name VARCHAR, Skipper VARCHAR, Points VARCHAR, Combined elapsed time VARCHAR) CREATE TABLE repeaters (repeaters_id AUTO_INCREMENT PRIMARY KEY, City of license VARCHAR, Identifier VARCHAR, Frequency VARCHAR, Power VARCHAR, Class VARCHAR, RECNet VARCHAR)  
SELECT COUNT Digital terrestrial channel FROM availability_of_channels_from_various_providers WHERE Channel = Channel 4